Power-operated percussive tools



Aug. 8, 1967 D, N. w. BADCOCK PowER-oPERATED PERcussIvE TooLs 5 Sheets-Sheet 1 Filed Oct. 19, 1964 DAVID N M Allg. 8, 1957 D. N. w. BADCOCK POWER-OPERATED PERCUSSIVE TOOLS 5 Sheets-Sheet 2 Filed OCT.. 19, 1964 erh/MM, iw(

ATTORNEXJ Aug# Y8, 1967 D. N. w. BADcocK 3,334,593

Filed Oct. 19, 1964 I5 Sheets-Sheet 3 im BY@ @mi TTORA/EYS DAVID N nl. BADcacK /NVENTOQ United States Patent 3,334,693 POWER-OPERATED PERCUSSIVE TOOLS David Norman William Badcock, London, England, as-

signor to Kango Electric Hammers Limited, London, England, a British company Filed Uct. 19, 1964, Ser. No. 404,595 Claims priority, application Great Britain, Oct. 23, 1963, 41,778/63 Z6 Claims. (Cl. 173-109) In another machine it has been arranged for the nose of the striker to engage some form of spring collet when the striker moves an appreciable distance beyond its normal blow-striking position.

In some electro-pneumatic hammers an idle running effect has been partially achieved by allowing air to pass through ports which are uncovered when the striker moves appreciably beyond the normal blow-striking position, but hitherto no provision has been made for trapping such air in a chamber formed between telescopically engaged striker and driver members.

A feature which, for convenience, may be referred to as momentary venting of the air space formed between striker and driver members has already been employed in percussive tools. The present applicant, for instance, has provided for such momentary venting in his U.S. Patent No. 2,880,585 by controlling the inow and outflow of air by the cooperation of at least one longitudinal groove in the exterior surface of the ydriver or the striker and of at least one annular groove in the interior surface of a cylinder which has an imperforate side wall and encloses or constitutes part of the coacting striker or driver.

The same momentary venting action has been obtained in a more recent 4proposal by providing an annular groove or recess within a ram-like hollow striker and employing therewith a piston having a thickness less than the width of such groove, so that air in a space on one side of said piston can ow to the other side of said piston as the latter passes over the groove.

The main object of the present invention is the provision of an improved hammer-type percussive tool having improved means adapted to allow of idle running of a striker member in` order to ensure that blows cease to be struck when the working implement is drawn clear of the work, although the motor or other power unit may still be in operation. This improved idle-running feature is applicable to a tool having a tool socket and to one without a tool socket.

The idle running means for achieving the abovementioned object of the present invention are particularly adapted for incorporation in an electrically-powered hammer and this application of the invention will be hereinafter more particularly described.

With a view to achieving the main object above-referred to the present invention provides a power-operated percussive tool comprising telescopically-engaged, relatively reciprocatable inner and outer cylindrical members forming an air chamber between them, means being provided for momentary venting said air chamber, both to allow air trapped therein to adjust to a substantially constant work- 3,334,693 Patented Aug. 8, 1967 ICC ing level during normal operation of the tool and also effectively to immobilise the outer member when this moves appreciably beyond its normal blow-striking position. The relatively reciprocatable members form the driverstriker components of the tool.

The inner member comprises or constitutes a sealing head on its inner end, said sealing head forming one end wall of the air chamber, whilst the other end wall thereof is formed by the closed end of the outer member. The outer member has two longitudinally-spaced internal annular recesses or wide grooves, the width of each recess being greater than the effective thickness of the sealing head, so that air on one side thereof can ow to the other side of said head, whenever said head passes over either of said recesses or grooves during relative reciprocation of the inner and outer members.

It will be understood that the above -requirements can be met in a sealing head of piston form having a cornparatively long skirt, as conveniently employed in electropneumatic hammers. In practise it is customary to relieve the barrel of a skirted piston, so that the crown end of the piston really forms the sealing head. Behind this relieving of the barrel a full diameter cylindrical surfaceor land is provided to guide the piston skirt. The sealing head may, however, be in the form of a narrow piston, as in the momentary venting arrangement already referred to, where the narrow piston would be less in thickness than the width of either of the two recesses or grooves.

Despite some alleged disadvantages possible in a skirted piston, we consider that this type of driver is particularly useful in that it augments the suction elfect by frictional drag, and thus during use tends to pull back the striker; this makes it possible to move a greater striking mass for any given cross section of air columnthat is, the cross section through the air chamber.

In prior formsof hammers having additional venting to provide idle running the admission of excess air served only to neutralise the negative pressure which no1'- mally causes the striker to move in sympathy with the piston or driver, but as this excess air was not trapped by the additional venting means the use of such a tool in an inverted position resulted in the strike dropping back to the normal working position under gravity action. This difliculty is avoided by the double recess venting which, whilst it still serves to neutralise the negative pull 'which normally tends to draw the striker back into the normal action range, also traps this excess air so that it becomes virtually impossible for the striker to resume its normal mode of movement until such time as the operator forces the striker back into the normal blow stri-king position by pushing the working implement against the work. When this has been eiected by normal cycle of operations recommences. Y

These advantageous results are secured by this invention because the momentary venting means now include an additional annular recess or groove in the striker, which may be called the idling recess and which is so positioned that it never comes into register with the sealing head (whatever form this takes) until such time as the striker moves out to near the limit allowed to it by the working implement or the holder therefor. Once the striker has taken up this position, although momentary venting will occur via the additional idling recess, the increased Volume of trapped air results in such a drastic reduction in negative pressure (when the piston or driver moves back) that the striker either remains stationary or else it adopts a harmless mode of movement of small amplitude. The excess air also ensures that the striker cannot accidentally resume a position where momentary venting occurs via the main or working recess.

The improved double-recess momentary venting provided by this invention is applicable equally to a percussive tool in which a tool or implement socket is employed or one in which the striker impacts directly on the shank of the working implement; in the latter case it is only necessary to allow for an adequate amount of outward movement of the working implement itself.

An electrically-powered percussive hammer incorporating the double-recess momentary venting above referred to will be hereinafter described, by way of example, when it will be more readily understood that this improved hammer embodies also a number of other advantageous features. These further features, however, have, in general, a wider eld of application, that is, these further irnproved features are not restricted to use in a tool employing momentary venting as broadly understood or as speciiically disclosed herein.

That is, the present invention has in view other objects, such as the provision of an improved tool assembly and of an improved layout of the component parts of the hammer, both of which render possible more eicient lubrication of the hammer mechanisms.

For instance, the present invention provides a percussive tool in which a tool rotating mechanism supported by the tool casing is employed which is driven by the driven means adapted to effect relative reciprocatory movement between said driver and striker components, a tool rotation drive shaft extending parallel to the longitudinal axis of said members.

The percussive tool described later herein is a multipurpose hammer in the sense that it provides for positive, torque-controlled rotation of one of a series of types of interchangeable working implements while the percussive blows vare being struck; this is of particular advantage when drilling or boring rock, concrete and similar hard materials. The improved form of hammer to be described is so constructed that the tool rotation means is always in action, even though it may not be coupled to the working implement; under these conditions there is an improvement in the blow-striking capabilities of the tool. In the tool construction hereinafter particularly described a slidable tool socket isV used, which is shaped to mesh with a toothed driving component forming part of the tool rotation mechanism, but the use of a tool socket is optional, in which case the tool itself-mounted with freedom for longitudinal sliding movement-would be directly engaged by said toothed driving component.

Thus in a preferred arrangement the tool rotating mechanism above referred to includes a tool socket adapted to receive and transmit impact blows from the striker of the tool and supported for rotatory and axial sliding movement at the outer end of the tool casing, said socket being adapted to receive interchangeable tools or tool adaptors, and motion transmission means driven by said driver shaft and co-acting with said socket to impart rotation thereto without interference with axial sliding movement of the socket. The motion transmission means may comprise a gear wheel held against axial displace- Vment and meshing -with a pinion on said drive shaft, said gear wheel being formed for driving engagement with the axially slidable tool socket. The driving engagement between said gear wheel and said socket is conveniently by means of a ratchet-like drive, and if desired this ratchet drive may comprise three spline faces on the tool socket adapted for co-acting with corresponding ratchet teeth inthe bore of said gear wheel, at least one socket spline making driving engagement with its associated gear wheel tooth Vin the event of misalignment of the socket and the wheel.

This invention, as already indicated, also provides an improved lay-out of the component parts of the hammer mechanisms. The object of the improved layout is to provide a tool which is more compact and better balanced than tools customarily employed, by reason in particular of the use of an in-line motor. Although several electric hammers proposed have had the motor arranged with its axis set at right angles to the longitudinal axis of the inter-operating striker and driver, at least one such hammer has used a motor which is coaxial with the driver-striker-tool axis. In this case, however, no toothed gear drive mechanism is included (or needed) between the motor and the in-line tool assembly; that is, this prior proposal was not an electro-pneumatic hammer. When such a drive mechanism has been employed in an electropneumatic hammer the axis of the motor has been offset from the driver-striker-tool axis, so that one side of the motor housing coud be substantially Hush with that part of the hammer casing which contains the driver and striker.

In one such arrangement the offset motor Vaxis has been aligned with the shaft of the tool rotating mechanism, said shaft extending parallel to the driver-striker axis.

The present invention goes further in seeking to improve tool balance by arranging the motor axis actually in line with the driver-striker axis. The transmission drive mechanism interposed between the motor, running at a comparatively high speed, and the slower'moving driver is nevertheless so compactly arranged that the whole of that drive mechanism aud the tool rotating mechanism, when used, can ybe enclosed in the same casing that contains the driver and striker and that supports the tool socket in the described embodiment, with the result that sump lubrication can be used in a fully enclosing casing.

Sump lubrication ensures the presence of oil mist Vin all parts of the enclosed casing, thus making it possible to use needle-roller and ball-bearings, and also to extend the life of many vital parts of the tool, such as a seal on the driver piston which would fail rapidly in efciency if allowed to run dry. In fact the only plain bearings that are used in the illustrative embodiment are those in the bore of a clutch gear (where fretting corrosion might cause damage) and in the tool socket itself, where the close t of the tool shank prevents the escape of oil in any appreciable amount.

In a tool where the tool casing is employed as a sump for lubricating oil the rotatable and slidable tool socket above referred to, may, as hereinafter particularly described, be constructed to serve as a means for sealing the tool end of the casing against leakage of oil.

The accompanying drawings illustrate, by way of example, one construction of electrically-powered percussive hammer according'to the invention which embodies essentially the double-recess momentary venting arrangement referred to, and incorporates also those additional advantageous features above mentioned, together with other useful features hereinafter described.

In the drawings:

FIGURE 1 is a part-sectional side elevation of the improved hammer;

FIGURE 2 is an enlarged longitudinal section on line y II-II of FIGURE 1, showing the striker, the skirted piston type driver and the double-recess venting;

FIGURE 3 is an enlarged cross-section on line III-III of FIGURE 1;

FIGURE 4 is an enlarged longitudinal sectional view of the tool socket and of part of the rotating means therefor; Y

FIGURE 5 is a cross-section on line V-V of FIG- URE 4;

FIGURE 6 is a side view looking in the direction of arrow VI in FIGURE 4; and

FIGURES 7, 8 and 9 are diagrammatic views of preferred coupling means between the tool socket and a toothed driving gear forming part of the tool rotating means.

In the embodiment illustrated in the accompanying drawings, the casing 1 which accommodates the mechanical components of the tool has directly mounted thereon the housing 2 ofan electric motor, aligned by means of 5 an interrupted register means, so that the central longitudinal axis X-Y is the common axis of rotation of the motor armature, of sliding of the driver and striker assembly and of the tool assembly. The motor may be of any suitable construction.

A toothed pinion 3 on one end of the motor armature shaft forms the first element of a speed reducing gear train and associated components which lie offset t the axis X-Y. The second gear train element is a larger diameter bevel crown wheel 4 to which is eccentrically coupled by connecting rod 5 a skirted piston 6 forming the driver of the tool. The drivel piston 6 telescopically engages a pot-like, that is, a closed-end, cylinder forming the striker of the tool, said striker cylinder 7 being free to float and reciprocate relatively to said piston 6, the cylinder being guided during reciprocation along axis X-Y by the bore 8 of casing 1 within which it slides.

Reciprocation of the driver piston 6 in the striker cylinder 7 causes this cylinder to reciprocate in casing 1 owing to the presence of a volume of air trapped between driver and striker. The resulting reciprocation of the striker cylinder 7 causes it in turn to strike the adjacent end of a tool or tool holder. The arrangement is well known and need not be described in detail herein. The volume of air is trapped in a variable capacity air chamber 9 defined within the imperforate -wall of striker cylinder 7 and between the closed-end 10 of said cylinder and the crown 11 of piston 6. inwards of piston crown 11 is a surface groove 12 from which extends along the piston skirt 13 at least one, but preferably a plurality of longitudinal grooves 14 which run out at the skirt rim. The portion 15 at the crown end of the piston beyond groove 12 4forms a sealing head, and approximately midway along the sealing head portion 15 is another groove 16 accommodating a resilient seal ring 17-of any suitable cross sectional form-adapted to make sealing contact with the bore 18 of striker cylinder 7. The striker bore 18 is interrupted by two annular recesses or grooves 19 and spaced longitudinally by an appropriate amount, the inner recess 19 being the main or working recess which corresponds to annular recess 4, 12 or 18 in the percussive tools illustrated in my aforesaid Patent No. 2,880,585. As explained in that patent the recess 19 serves to vent the air chamber 9 momentarily at certain points in the cycle of operations with the result that the volume of air contained therein adjusts itself to a substantially constant level during normal operation despite leakage which occurs at times when the chamber should be sealed. Moreover, since venting occurs when the driver is at the bottom of its stroke any excess air is discharged and the resulting negative pressure in the chamber on the up stroke of the driver causes the striker to follow.

The other internal annular recess 20 is an auxiliary or idling recess.

From FIGURE 3 it will be seen that the annular recess 19 is discontinuous and is actually comprised of a series of circumferentially spaced pockets 19A. The striker cylinder 7 is relieved intermediately of its length to provide a waist 7A of slightly reduced diameter and the bore 8 of casing 1, along which slide the full diameter cylindrical lands 7B, 7C of striker cylinder 7, is provided with longitudinal utes 8A.

The purpose of the recess 20 is to ensure that blows cease to be struck when the tool is drawn clear of the work even though the motor is still operating. When the constraint of the tool on the striker is removed it moves outwards beyond its normal range of movement. It is then not possible for the recess 19 to register with the groove 12 on piston `6 with the result that excess air cannot be discharged. The striker is thus moved outwardly to its full extent and at the top of the stroke of the driver its groove 12 will register with recess 20 so that air can enter the chamber 9 should there be any negative pressure therein. The striker will consequently remain in this position however the tool is held until it is again applied to the work and the striker pushed inwards.

The connecting rod 5 is directly pivotally connected to a crank pin 21 on crown wheel 4 and to a gudgeon pin 22 in the piston 6; that is, without the interpositioning of a cross head.

Parallel to axis X-Y and as close to striker cylinder 7 as is conveniently practicable is a shaft 23 forming part of a tool rotating mechanism and adapted to derive rotary motion from the shaft 24 of crown wheel 4, journalled in bracket bearing 25 conveniently mounted on the motor housing 2. This motion is transmitted through mating bevel pinions 26, 27 and spur wheels 28, 29 via an overload clutch 30. The clutch 30 is of compact form and comprises a pack of waved or corrugated springy washers 31 interposed between a backing plate 32, clamped to, and rotating with pinion 27 and keyed to friction disc 33, on one side of spur wheel 28. 'Ihe clutching action is due to springy washers 31 pressing friction disc 33 against wheel 28 (capable of limited axial displacement) and this onto another friction disc 34 which rests against and is keyed to the ange of a sleeve 35 encircling and secured to the spigot of pinion 27.

It will be seen from FIGURE 3 that the tool rotating shaft 23 extends for part of its length through a channel 1A forming an integral part of the casing 1 and is in open communication therewith, and from FIGURE l it will be seen that the close disposition of shaft 23 to the driver-striker cylinder and the compactness of the motion transmission mechanism permit of the accommodation of the driver-striker assembly, of shaft 23 and of said transmission mechanism in the single common casing 1, so that sump lubrication can be employed.

The blow transmitting and tool holding assembly in the illustrated embodiment comprises a hollow holder S0 secured in any suitable manner to casing 1, the fiange 51 of a recoil buffer housing 52 being interposed between the opposed open ends of said holder and said casing. The housing 52 supports a ball race 53 which affords bearing support to a tool socket 54, the inner end of which projects into casing 1 and constitutes an anvil 55 adapted to receive impact blows from striker cylinder 7.

The outer end 56 of socket 54 is hollowed to receive the shank of a tool, or, as shown, a tool adaptor 57, the forwardly projecting tool-holding end of which is supported in a cap 58 screwed into the front end of holder 50. The bores of socket end 56 and of cap 58 are conveniently of hexagonal shape in cross section, although the adaptor 57 itself is not necessarily of complementary form.

A swing-over handle 59 is mounted exteriorly of cap 58 on a latching rod 60 rockably supported within said cap and adapted to normally allow a degree of longitudinal displacement of the adaptor 57 but to prevent its complete release, which can be effected at will by rocking rod 60 (by means of handle 59) to position a fiat 61 thereon so as to allow the adaptor to pass out of cap 58.

The intermediate waist 62 of tool socket 54 is of ratchet form in cross section and slidably engages the splined bore 63 of a toothed spur wheel 64, which, when holder 50 is assembled on casing 1, meshes with a pinion 65 on the projecting end of tool rotating shaft 23. Spur wheel 64 is supported by ball races 66 and 67, the former bearing against the buffer housing 51 and the latter bearing against a sleeve-like cage 68 which is backed-up by spring loading means 69 comprising, for instance, a pack of waved washers; this mode of assembly provides compensation for manufacturing variations and for wear.

The tool- (or adaptor) receiving end 56 of tool socket 54 is encompassed by a replaceable bush 70 locked by a nut and supported by an internal partition 71 in holder 50, and this bush is gripped by a dust-excluding rubber sleeve 72 firmly anchored to the outer end of socket 54. It will be seen that the inner part of holder 50 (that is, inboard of partition 71) is in open communication with the shaft channel 1A through an opening 151 in the flange 51 of the buffer housing 52, and thus with 7 the interior of casing 1 which forms a sump for lubrieating oil, so that oil can lubricate spur wheel 64 and pinion 65 but cannot escape through bush 70 because of the close t between bush 70 and tool holding member 56; the casing 1 has an oil ller cap 73.

The loading washers 69 are interposed between one end of cap 68 and a nut 170 screwed onto the spigoted end of bush 70.

It will be appreciated that the rotatable tool socket 54, largely by means of its lengthy bearing surface within bush 70, serves to seal the holder S (which is a continuation of casing 1) against the escape of lubricating oil from the sump constituted by the casing and the cornmunicating interior of holder 50. This use of the socket 54 as an oil seal renders unnecessary the provision of separate means for this purpose.

The ratchet and spline connection between the waist 62 of tool socket 54 and the spur wheel 64 provides for self-aligning of the tool socket during its rotation. FIG- URE'7 illustrates the ideal operating condition where each of the three ratchet teeth 62A, 62B and 62C of the tool socket share equally the torque loading applied t-o the respective spline faces 64A, 64B and 64C of spur wheel 64; the contact band Z is theoretically uniform and there is equal backlash clearance x between faces of the socket and the spur wheel perpendicular to the ratchet teeth and spline faces.

FIGURE 8 shows how misalignment of tool socket and spur wheel of a magnitude y (for instance, about .010 inch) imposes the driving load on a single ratchet tooth 62A and the mating spline face 64A, with consequential reduction of backlash clearance x; line R indicates the approximate direction of reaction of driving. FIGURE 9 shows the conditions 60 later than FIGURE 8, where now the mating teeth and splines 62A, 62C and 64A and 64C equally share the loading at this particular instant, Ibut with load increasing between 62A and 64C and decreasing between 64A and 64C.

It will be understood that as long as any misalignment exists the drive will never be taken on more than two spline faces at any given instant and that the drive will pass from one face to the next to distribute wear evenly over all three faces. Wear of the tool socket bearings and of the stationary races of the spur wheel 64 will tend to reduce misalignment, and resulting further wear of these bearings. It will be seen als-o that misalignment tends to reduce backlash and it will be appreciated that the driven and driving faces concerned will be subject to radial sliding (equal to twice the misalignment) and to rocking Errors of division will result in concentration of the load and of the wear and there will be a tendency to correction of the errors.

It will also be understood that in the embodiment illustrated the ratchet and spline coupling on the one hand ensures positive driving of the tool socket, whilst on the other hand allowing freedom of relative sliding in an axial direction to any extent necessary in practice to allow of the idle running action already referred to.

I claim:

1. A percussive tool comprising a casing, telescopically-engaged, relatively reciprocatable driver and striker members within said casing and forming an air chamber between them, means for momentary venting said air chamber both to allow air trapped therein to adjust to a substantially constant working level during normal operation of the tool and also effectively to immobilize said striker member when this moves appreciably beyond its normal blow-striking position, and power means on said casing for operating said driver member.

2.'A power-operated percussive tool comprising a casing, telescopically-engaged relatively reciprocatable driver and striker members within said casing slidable one within the other to form an air chamber between them, the inner end of said inner member comprising a sealing head and thus forming one end wall of the air chamber, the other end wall thereof being formed by the closed end of said outer member, said outer member having two axially spaced internal annular recesses each having a width greater than the effective axial width .of said sealing head, said recesses allowing air on one side of said head -to flow to the other side thereof whenever said head passes over either of said recesses during relative reciprocation of said inner and outer members, and means for effecting reciprocation of said driver member.

3. A percussive tool as claimed in claim 2, wherein said sealing head is provided by the use of an inner member in the form of a long skirted piston.

4. A percussive tool as claimed in claim 2, wherein said sealing head is provided by the use of an inner member in the form of a narrow piston, that is, one of a thickness less than the width of either of the two recesses or grooves.

5. A percussive tool as claimed in claim 1, in which said power means is an electric motor having the motor axis in line with the longitudinal axis of said relative- =ly reciprocatable members.

6. A percussive tool, as claimed in claim 1, including a tool rotating mechanism supported by said casing and driven by said power means, said mechanism including a tool rotation drive shaft extending parallel to the longitudinal axis of said relatively reciprocatable members.

7. A power-operated percussive tool comprising a casing, a telescopically-engaged, relatively reciprocatable cylindrical driver and striker within said casing and forming an air chamber therebetween, means in said striker for momentary venting said air chamber -to allow air trapped therein to adjust to a substantially constant working level during normal operation of the tool and also effectively to immobilize the striker when this moves appreciably beyond its normal blow-striking position, an electric motor mounted on one end of said casing, tool rotating mechanism supported on the other end lof said casing, drive means on said casing driven by said motor for effecting relative reciprocatory movement between said driver and striker and a tool rotation drive shaft extending parallel to the longitudinal driver-striker axis.

8. A percussive tool as claimed in claim 7, wherein said tool rotating mechanism includes a tool socket adapted to receive and transmit impact blows from said striker and supported for rotatory and axial sliding movement at said other end of said casing, said socket being adapted to receive interchangeable tools or tool adaptors, and motion transmission means driven by said drive shaft and co-acting with said vsocket to impart rotation thereto without interference with axial sliding movement of said socket.

9. A percussive tool as claimed in claim 7, wherein said driver is in the form of a long skirted piston.

10. Apercussive t-ool as claimed in claim 7, characterised in that the motor axis is in line with the longitudinal axis of the relatively reciprocatable driver and striker.

11. A power-operated percussive tool comprising a casing, a striker slidable within said casing, a driver of long-skirted piston form, telescopically-engaging said striker and relatively reciprocatable therein to form an air chamber therebetween, said striker having two longitudinally-spaced internal annular recess, and said driver constituting by its inner end a sealing head which forms one end wall of said air chamber, the other end wall thereof being formed by the closed end of said striker, each said striker recess having a width greater than the effective 'axial width of said sealing head, an electric motor mounted on one end of said casing with its longitudinal axis in line with the longitudinal axis of the relatively reciprocatable driver and striker, a tool mechanism supported by the other end of said casing, drive means in said casing driven by said motor to effect relative reciprocatory movement between said driver and striker said tool mechanism including a tool socket providing a leak-proof closure for said other end of said casing, whereby said casing serves as a sump for lubricating oil.

12. A percussive tool as claimed in claim 11, wherein said tool socket is rotatably mounted in said casing and a rotation drive shaft extends parallel to the longitudinal axis of said driver and striker within said casing, said drive shaft being rotatable by said motor-driven drive means.

13. A power-operated percussive tool, comprising a casing, a relatively reciprocatable telescopicallyengaging driver and striker, in said casing, a tool socket rotatably and slidably mounted on one end of said casing, a tool rotating shaft within said casing, an electric motor on the other end of said casing, and drive means housed within said casing for effecting relative reciprocation between said driver and striker and for rotating said shaft.

14. A percussive tool as claimed in claim 13, in which said tool socket serves as a means for sealing the tool end of the casing to enable the casing interior to be used as a sump for lubricating oil.

15. A power-operated percussive tool, comprising a casing, an electric motor mounted on one end of said casing, a tool mechanism supported by the other end of said casing and including a tool socket supported for rotatory and axial sliding movement in said other end of said casing and a tool socket rotating shaft, a relatively reciprocatable telescopically-engaging driver and striker in said casing, motion transmission means within .the casing adjacent said motor for effecting relative reciprocatory movement between said driver and striker and for driving said tool socket rotating shaft, the axis of said shaft extending parallel to the longitudinal axis of said components.

16. A percussive tool as claimed in claim 15, said socket being adapted to receive interchangeable tools or tool adaptors, and driving means coupling said tool socket rotating shaft and said socket to impart rotation to said socket without interfering with the axial sliding movement thereof.

17. A percussive tool as claimed in claim 16, in which said driving means comprises a gear Wheel held against axial displacement and meshing with a pinion on said tool socket rotating shaft, said gear wheel being formed for driving engagement with the axially slidable tool socket.

18. A percussive tool as claimed in claim 17, wherein the driving engagement between said gear wheel and said socket is by means of a ratchet-like drive, which comprises three spline faces on the tool socket adapted for co-acting with corresponding ratchet teeth in the bore of said gear wheel, at least one socket spline making driving engagement with its associated gear wheel tooth in the event of misalig'nment of the socket and the gear wheel.

19. A power-operated percussive tool, comprising a casing, a telescopically-engaged relatively reciproca-table driver and striker within said casing, a power unit on one end of said casing, a tool rotating mechanism on the other end of said casing and including a tool socket for receiving and transmitting impact blows from the striker and supported for rotatory and axial sliding movement at said other end of the casing, said socket being adapted to receive interchangeable tools or tool adaptors, and motion transmission means driven by said power unit and co-acting with said socket to impart rotation thereto without interference with axial sliding movement of the socket.

20. A percussive tool as claimed in claim 19, in which said motion transmission means comprises a drive shaft, a gear wheel held against axial displacement and meshing with a pinion on said drive shaft, said gear Wheel -being formed for driving engagement with the axially slidable tool socket.

21. A percussive tool as claimed in claim 20, wherein the driving engagement between said gear wheel and said socket is by means of a ratchet-like drive which comprises three spline faces on said tool socket coacting with corresponding ratchet teeth in the bore of said gear Wheel, at least one socket spline making driving engagement with its associated gear wheel tooth in the event of misalignment of the socket and wheel.

22. A percussive tool as claimed in claim 21, wherein the relatively reciprocatable driver and striker, the drive shaft and the motion transmission means are housed in a common casing.

23. A percussive tool as claimed in claim 22, in which the rotatable and slidable tool socket serves as a means for sealing Athe tool end of the casing to enable the casing interior to be used as a sump for lubricating oil.

24. A percussive tool as claimed in claim 19, including a tool holder secured to said other end of said casing with the interposition of a housing for a recoil buffer for the tool socket, the inner end of said tool socket, which serves as an anvil to receive impact blows from said striker, projecting through said housing into the casing interior, and the outer end of said tool socket extending through an elongated bush supported by a partition within said holder, the interior of the holder inwards of said partition accommodating said motion transmission means.

25. A percussive tool as claimed in claim 24, wherein' that portion of the holder interior accommodating said motion transmission means is in open communication with the casing interior for admission of said holder portion of lubricating oil from the sump-forming casing.

26. A percussive tool as claimed in claim 19, in which said motion transmission means includes an overload clutch.

References Cited UNITED STATES PATENTS 1,92l,628 8/1933 Maxwell et al. 173-109 2,458,289 l/ 1949 Morrison 173-133 2,536,971 1/1951 Weyandt et al 173-132 2,588,360 3/1952 Cole 173-132 2,880,585 4/1959 BadCOck 173-118 3,170,523 2/1965 Short 173-104 3,203,490 8/ 1965 McCarty et al. 173-109 3,269,466 8/ 1966 Mitchell 173-116 FRED C. MATTERN, JR., Primary Examiner.

L. P. KESSLER, Assistant Examiner. 

7. A POWER-OPERATED PERCUSSIVE TOOL COMPRISING A CASING, A TELESCOPICALLY-ENGAGED, RELATIVELY RECIPROCATABLE CYLINDRICAL DRIVER AND STRIKER WITHIN SAID CASING AND FORMING AN AIR CHAMBER THEREBETWEEN, MEANS IN SAID STRIKER FOR MOMENTARY VENTING SAID AIR CHAMBER TO ALLOW AIR TRAPPED THEREIN TO ADJUST TO A SUBSTANTIALLY CONSTANT WORKING LEVEL DURING NORMAL OPERATION OF THE TOOL AND ALSO EFFECTIVELY TO IMMOBILIZE THE STRIKER WHEN THIS MOVES APPRECIABLY BEYOND ITS NORMAL BLOW-STRIKING POSITION, AN ELECTRIC MOTOR MOUNTED ON ONE END OF SAID CASING, TOOL ROTATING MECHANISM SUPPORTED ON THE OTHER END OF SAID CASING, DRIVE MEANS ON SAID CASING DRIVEN BY SAID MOTOR FOR EFFECTING RELATIVE RECIPOCATORY MOVEMENT BETWEEN SAID DRIVER AND STRIKER AND A TOOL ROTATION DRIVE SHAFT EXTENDING PARALLEL TO THE LONGITUDINAL DRIVER-STRIKER AXIS. 